TNF and Arthritis: Pro-inflammatory cytokines, including interleukin (IL)-6, IL-8, IL-15, IL-17, IL-18, IL-21, IL-1β, IL-33, and tumor necrosis factor (TNF)-α, and anti-inflammatory cytokines, such as IL-4, IL-10, IL-13, and IL-37, play an important role in the pathogenesis of arthritis [6,7,8,9,10,11,12].